Internal combustion engine or compressor

ABSTRACT

The invention concerns a double acting engine which may be either an internal combustion engine or a compressor, the construction being characterized by the combination of a main cylinder, a double-acting type piston reciprocatably mounted therein, a cylinder head detachably mounted on each end of the main cylinder and carrying a cylindrical sleeve of smaller diameter than the main cylinder and extending coaxially towards the main cylinder, a hollow portion of reduced diameter extending coaxially from each end of the main piston to slidably fit within said cylindrical sleeve extending towards it, valve means to control the admission of air to the annular main cylinder space surrounding said hollow reduced portion, inlet valve means mounted on said piston to control the admission of air from said annular cylinder space into said hollow portion of the piston, outlet valve means mounted on said piston to control the transfer of air from said hollow piston portion into the interior of said sleeve, and exhaust valve means in the cylinder head to control the discharge of exhaust gas from said sleeve. The construction may also incorporate an auxiliary piston slidable in each of the aforesaid sleeves, the movements of the auxiliary pistons being constrained so that for the major part of their travel they move in opposition to the main piston. The latter is operatively connected directly to a crank shaft without the intermediary of a connecting rod and the movements of the auxiliary pistons are coordinated from the crankshaft through the intermediary of suitable connecting links, the arrangement permitting fine adjustment. The construction and arrangement of the valves is such that, when used as an internal combustion engine, air passes into the engine by way of an outer annular air chest and after its initial compression progresses through the engine interior in a generally axial direction to final exhaust. This not only greatly simplifies the flow of the motive fluids but facilitates cooling and gives ample cylinder strength at all parts, resulting in overall efficiency and economy in production.

United States Patent Walls [4511, ept- 6. 9.72

[ 1 INTERNAL COMBUSTION ENGINE OR COMPRESSOR [72] Inventor: Patrick Joseph Walls, Rosemount Glandore Road, Dublin 9, Ireland [22] Filed: Dec. 9, 1970 [21] Appl. No.: 96,330

[52] U.S.Cl. ..4l7/26l,4l7/5lO,91/l56 [51] Int. Cl ..F04b 3/00, F04b 5/00, F04b 25/00,

F04b 7/00, FOlb 1/00 [58] Field of Search ..4l7/246, 510, 254, 259, 261;

FOREIGN PATENTS OR APPLICATIONS 335,859 10/1930 Great Britain ..9l/l56 Primary Examiner-Robert M. Walker Attorney-Mason, Fenwick & Lawrence [57] ABSTRACT The invention concerns a double acting engine which may be either an internal combustion engine or a compressor, the construction being characterized by the combination of a main cylinder, a double-acting I type piston reciprocatably mounted therein, a cylinder head detachably mounted on each endof the main cylinder and carrying a cylindrical sleeve of smaller diameter than the main cylinder and extending coaxially towards the main cylinder, a hollow portion of reduced diameter extending coaxially from each end of the main piston to slidably fit within said cylindrical sleeve extending towards it, valve means to control the admission of air to the annular main cylinder space surrounding said hollow reduced portion, inlet valve means mounted on said piston to control the admission of air from said annular cylinder space into said hollow portion of the piston, outlet valve means mounted on said piston to control the transfer of air from said hollow piston portion into the interior of said sleeve, and exhaust valve means in the cylinder head to control the discharge of exhaust gas from said sleeve. The construction may also incorporate an auxiliary piston slidable in each of the aforesaid sleeves, the movements of the auxiliary pistons being constrained so that for the major part of their travel they move in opposition to the main piston. The latter is operatively connected directly to a crank shaft without the intermediary of a connecting rod and the movements of the auxiliary pistons are co-ordinated from the crankshaft through the intermediary of suitable connecting links, the arrangement permitting fine adjustment. The construction and arrangement of the valves is such that, when used as an internal combustion engine, air passes into the engine by way of an outer annular air chest and after its initial compression progresses through the engine interior in a generally axial direction to final exhaust. This not only greatly simplifies the flow of the motive fluids but facilitates cooling and gives ample cylinder strength at all parts, resulting in overall efficiency and economy in productron.

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1 WN l w m Ii an M K m m m PATENTEDSEPZS I912 SHEET 7 BF 8 Inventor DA-rmcK 3o5F=PH WALLs was M fi hw Attorneys INTERNAL COMBUSTION ENGINE OR COMPRESSOR 1 BACKGROUND OF THE INVENTION hereinafter be made apparent. It is well known that many engines could equally be used as compressors if driven by applying external forces thereto, and consequently the term engine used herein is to be taken as including a device of similar construction when driven by external forces instead of by the action of internal combustion. Similarly a reference to air is intended to include any other suitable gas. where the context so admits.

In general, the invention concerns engines of the kind having a double-acting piston, each end face of which is associated with at least two cylinder spaces one of which is arranged concentrically with respect to the other, and having valve means, controlling the transfer of compressed air from one cylinder space to the other. The principal features of the'invention are applicable toengines having a free piston aswell asto engines in which the piston is connected by appropriatedriving mechanism to acrankshaft or other means for converting reciprocating motion into rotary motion.

The object of the invention is to provide an improved construction of engine of thekind referred to which will be compact, smooth running and efficient and which has many other advantages, aswill be apparent from the following description,.including particularly the possibility of readily adapting the engine to runon different fuels, e.g. on gasolene or on diesel oil.

SUMMARY OF THE INVENTION According to the. invention, an engine of the kind referred to comprises a casing cylindrically bored to provide a main cylinder in which a piston (hereinafter termed the main piston) is adapted to reciprocate, each end of said cylinder having a detachable. head or guide cover carrying a cylindrical sleeve of smaller internal diameter than the main cylinder and extending coaxially towards or into the end of the main cylinder, the main piston having an extension of reduced diameter projecting from each end thereof and slidable. within the sleeve of the adjacent head or guide cover, said extension being hollow and affording a transfer chamber with valve-controlled inlet and outlet ports whereby air compressed by the main piston may be passed through the transfer chamber into the. sleeve, further compressed therein, and eventually exhausted through the cylinder head or guide cover.

When operated as an internal combustion engine, the air compressed within the sleeve provides, when mixed with fuel, the combustible mixture and combustion takes place within the sleeve each time the latter is charged. Thus, since compression occurs alternately in the sleeves on opposite sides of the piston, the latter is positively driven by combustion of the charge on one side or the other at every stroke.

In one proposed construction according to the invention, an auxiliary piston is provided in each sleeve, the

two auxiliary pistons are yoked together so as the ordinating the movements of the main piston previously referred to above and the auxiliary pistons so that they are timed to move in opposite directions at all times, with-the possible exception of a very short period when the pistons are approximately at their dead center positions.

The auxiliary pistons are similarly connected to the crankshaft through the'intermediary of the yoke device and this arrangement is carried out in such a way that the parts are substantially balanced both statically and dynamically.

In the arrangement last described, employingauxiliary pistons, according to a further feature of the invention the exhaust gases are adapted to be expelled from the combustion chamber through the auxiliary pistons, which are of tubular construction, by way of a valvecontrolled exhaust aperture, and means may also be provided for adjusting the operation of said exhaust valve.

In order that the invention may be more readily and fully understood referenceis made to the accompanying drawings.

IN THE DRAWINGS FIG. 1 is a vertical section taken through the axis of the main cylinder of one construction of engine according to the invention;

FIG. 2 is a vertical cross-section on line II--II of FIG. 1 (some minor parts being omitted for the sake of clariy);

FIGS. 3 and 4 show to an enlarged scale details of the valve gear of the engine shown in FIGS. 1 and 2, FIG. 3 being a plan viewed substantially on line III-III ofFIG. l, and FIG. 4 an elevation partly in'cross-section corresponding to line IV-IV of FIG. 3;

FIG. 5 is a sectional plan view showing a further construction of engine according to the invention, only the left hand portion of the engine being shown,

FIG. 6 is an enlarged cross-section of an alternative form of auxiliary piston for the engine shown in FIG. 5;

FIGS. 7, 8 and 9 show to an enlarged scale details of portion of the valve gear of the engine shown in FIG. 5, FIG. 7 being a front elevation, FIG. 8 an end view and FIG. 9 a plan,

FIGS. 10, 11 and 12 are respectively a front elevation, side elevation and rear elevation of a detail of FIG. 5 to an enlarged scale;

FIG. 13 and 14 are respectively a plan and front elevation of. further details of FIG. 5 to an enlarged scale;

FIGS. 15 and 16 are diagrammatic representations of the complete engine constructed according to FIGS. 1 to 4, FIG. 15 being a plan showingthe piston at one end of a stroke, and FIG. 16 being a corresponding elevation, and

FIGS. 11 and 18 are similar diagrammatic representations of the engine constructed according to FIGS. 5 to 14.

Corresponding parts are indicated by similar reference numerals in all the views.

Referring to FIGS. 1 to 4, the engine shown cornprises a cylindrically bored casing 1 constituting the main cylinder, mounted upon, and preferably integral with, a crank case 2, the interior of which communicates with the interior of the casing l by way of a slot 3. The cylindrical bore of the casing 1 is preferably provided with a liner 4 in which the main,piston 5 is adapted to slide.

The opposite ends of the piston 5 each have an annular face 6 and an extension 7 of reduced diameter, hollowed to provide a transfer chamber 8. The extension 7 is adapted to slide in a cylindrical sleeve 10 projecting axially from a detachable head-or guide cover 11 which is bolted to the casing. 1, avalvering 12 formed with a number of port apertures 13 (FIG. 3) being interposed between the head 11 and the main cylinder casing l.

The head 11 is closed by a cap 1 la formed externally with cooling fins and provides an annular air inlet chest 14 with an inlet opening 15. The valve ring 12 obturates passages 9 which when uncovered by the apertures 13 of the valve ring permit air to pass from the chest {14 intothe annular air compression space 16. The latter communicates by way of inlet port 17 with the chamber 8 when a valve 18 obturating said port is open. The valve 18 acts as a non-return valve and is biassed towards its closed position by a spring 19. A poppet valve 20, also spring loaded, is seated upon the outlet port 21 leading from the chamber 8'into the cylinder space 22 of the sleeve 10 providing the combustion chamber of the engine. The exhaustport 23 of the combustion chamber is closed by a mushroom valve 24 guided in the head portion 11a and adapted to be operated by valve gear (shown by broken lines in FIG. .1) comprising a rocking lever 25 pivoted intermediately to a link 27 and actuated by the rod 26 as hereinafter described with reference to FIGS. 15 and Both ends of the cylindrical casing 1 are similarly constructed and equipped. As already stated above, the engine may be used as afree piston engine, but when used to drive a crankshaft the piston 5 is advantageously connected with a crankshaft 30 journalled in the-casing 2, through the intermediary of a slide block 31, in which the crank pin '32 is journalled and which is slidable transversely in the piston 5.

The operation of the exhaust valves 24 is derived from the crank shaft 30, and in the arrangement shown more clearly in FIGS. 15 and 16 this is effected by a cam groove in a cam device 36, which also has a flywheel effect, mounted on .the crankshaft 30. The

rods 26 are pivoted to bell crank levers 37 carrying cam rollers (not shown) which engage'the cam groove 35," as will .be readily understood from FIG. 15. It will be seen that by this arrangement the rods 26 are moved alternately in the opposite direction to that in which the piston'5 is travelling, so as to open the exhaust valve 24 away from which the piston 5 is moving near the end of its stroke, said valve being closed again as the piston returns.

The operation of the air inlet valve ring 12 is ad vantageously effected by mechanism shown more clearly in FIGS. 3 and 4. The ring 12 which consists of a flat plate is held in position adjacent to the air inlet passages 9 (FIG. 1) of the air chest 14 by means of a collar 12a screwed on the end of the sleevel0 and permitting the ring to be freely rotatable. The passages 9 are shaped and arranged so that in one position of the ring 12 they coincide with th'e c brresponding apertures 13 of said ring, while if the "ring'is rotated through a predetermined angle (15 with the example shown in FIG. 3) the apertures 13-are moved out of coincidence with the passages which are then'completely closed by the ring v 12. THe latter is adapted to .be oscillated through the angle in question in synchronism with the movement of the piston 5 by means of thecylindrical cam 36 on the crankshaft '30, said cam having a cam groove 82 in which engages a roller 83 carried by an arm 34 on one end of a spindle 40 journalled in the case 1 and-having on its other end a toothed quadrant 41' which engages a correspondingly toothed portion 42 The the valveplate ring 12. The shape of the cam groove 82 is designed to ensure that 'the'ring 12 is moved to uncover the air passages 9 at the appropriate time relatively to the position of the piston 5' in the course of its stroke, and to close said passages to cut off the entry of air during the periods of the cycle of operations when it is required to compress the air which has passed into the annular air compression space 16.

If desired the cam groove 82 may also be' utilized to operate an oil pump 96 for lubrication purposes arranged in the sump as indicated in FIG. 2, the spindle 44 rotatable mounted in said sump or an adjacent part of the engine casing 1 having on its upper end an arm 45 carrying a roller (not shown) for engagement with said cam groove in a similar manner to the roller 83 above mentioned, and on itsother end a fork 46 engaging an operative part of the pump 96 to reciprocate the latter in well known manner.

In the case where the engine is to be driven by fuel oil, such as diesel oil injected periodically into the cylinder spaces 22 by way of an injection device (not shown) of known form arranged in the head 11, the crankshaft 30 maybe adapted to drive a fuel pump, for example as shown in FIG. 2, wherein pump plungers (not shown) are adapted to be reciprocated in cylinder 39 by a cam 40 on the shaft 30. The way in which the fuel pump in constructed and operated forms no part of the present invention and does not require to be further described.

The engine operates as follows Consider first the left hand portion of the engine as viewed in FIG. 1. The piston 5 may be assumed to be moving from right to left (the crank .30 rotating clockwise). Air which on the previous stroke, when the piston moved towards the right, was drawn in from opening 15 and air chest 14 through the valve ports 13 into the cylinder space 16, will now be compressed by the piston 5, the valve port '13 being closed by partial rotation of the valve ring 12, and the air under pressure is then driven through ports 17 (valve 18 beingforced open) and into the chamber 8, the valve 20 being meanwhile held upon its seating by the loading of its spring 19a. The pressure in the combustion space 22 will, however, be relatively low as the exhaust valve 24 will have been previously opened by operation of the valve mechanism 36, .37, 26, 25 as already described. The valve 20 therefore opens, and air under pressure is drivenfrom the chamber 8 into the combusting space 22, where it performs initially a scavenging action assisting the expulsion of the combustion products from the combustion space 22. At a suitable point, however, the valve 24 is closed by the operation of the aforesaid valve mechanism and'when the pressure of the air trapped in the space 22 approaches that of the air in the chamber 8 the valve 20 closes and further movement of the piston towards the left increases the pressure of the air charge within the space 22. At a suitable point, when the piston 5 is at or very near the end of its stroke fuel is injected into the space 22, combustion takes place therein and the piston is driven on its return stroke to the right. During this stroke a fresh charge of air is drawn from the air chest 14, past valve ports 13 into the air compression space 16, the valve 18 also being closed by the spring 19 assisted by the inertia effect upon the valve 18 as the piston reverses its direction of motion. The cycle of operations is thus completed, the exhaust 24 being opened at a suitable point towards the end of the stroke.

n the other side of the piston the operations above described also take place, but the operations are timed approximately 180 out of phase therewith, considered in relation to the position of the crankshaft 30. It is observed, however, that every stroke of the piston is a driving stroke.

If the engine is to be run on petrol, instead of Diesel oil or the like heavy oil it is only necessary to change the cylinder head 11 for others in which provision is made to introduce a sparking plug, in which event the pump 39 may be dispensed with (or used merely to supply oil under pressure for lubrication), and a magneto or other known means for producing the necessary ignition suitably installed. The compression ratio in any case may be determined by the thickness of the valve ring 12, which is also exchangeable.

If the engine is to be run as a compressor the cylinder heads 11 are preferably replaced by a modified head in which the valve 24 is replaced by a spring loaded relief valve. In this case the compression ratio of the space 22, which then becomes a final stage compression cylinder may be chosen as desired and the exhaust valve may be arranged to open outwardly of the compression cylinder, under the automatic control of its spring, suitably chosen so as to ensure delivery of the air at a predetermined pressure. In this case the engine is preferably driven by external means coupled to the crankshaft, but it would also be possible to operate the engine partly as a compressor and partly as an internal combustion engine, using one of the cylinder spaces 22 as a combustion space and the other purely for compression and supply of compressed air, provided that a flywheel of adequate size or other means is provided to maintain the smooth rotation of the crankshaft.

An important feature of the engine constructed as above described lies in the fact that the parts are very effectively air-cooled, cold air being first drawn into the air chest 14 surrounding the sleeve 10 in which combustion takes place, and then flowing through the casing l, the body of the piston 5 and the extension 7 thereof which constitutes the transfer chamber, so that it enters the combustion space 22 in a somewhat preheated condition. The cylinder heads 11 and the exhaust passages therein are also adequately finned to assist in the cooling of these parts, but they may be provided with cooling water jackets if desired.

Referring now more particularly to the modified construction of engine according to the invention shown in FIG. 5 and diagrammatically in FIGS. 17 and 18, the middle portion of the engine, as seen in FIG. 5 is almost identical with that described above. Instead of a fixed head being provided for the combustion spaces 22,

within the sleeves 10, however, auxiliary pistons are slidable in said sleeves, said pistons being disposed coaxially at opposite sides of the main piston 5 and being yoked together by the aid of cross beams 51 and links 59 connecting said cross beams with members 52 rotatably mounted on crank pins 53 on the crankshaft so that the links 59 of the respective cross beams 51 are arranged to operate l80 out of phase therewith. In other words a four-journal crankshaft is provided (FIGS. 5 and 17), the central journal 54 carrying the slide block 31 which is slidable transversely relatively to the piston 5, while the crank pins 53 are displaced 180 with respect to the crank pin 32. The general arrangement is shown diagrammatically in FIGS. 17 and 18.

As a result of this arrangement the pistons 50 are constrained to move in synchronism with the piston 5, but in the opposite direction. The sizes and weights of the pistons and the mechanisms respectively connected therewith are advantageously designed so that they are completely balanced both statically and dynamically.

An important feature of the engine shown in FIG. 5 lies in the fact that the gases exhausted from the combustion (or compression) spaces 22 pass out by way of the auxiliary piston 50. As shown in FIG. 5 the cover 11 provides a guide portion 60 for the tail end of the piston 50 which is tubular, and the exhaust valve 24 is slidably mounted on a cross piece 61 in the piston 50 which in turn is secured to the cross beam 51.

The valve 24 is adapted to be operated in accordance with the position of the piston 50 in the course of its stroke. For this purpose, and also to permit of adjusent in the timing, the mechanism shown in FIGS. 7 to 14 may be employed. Parts of this mechanism are also shown in FIG. 5 but some parts are omitted in the interest of clarity. The valve 24 is carried by a spindle 62 which passes through a slot 63 in the cross-piece 61 so that its ends project beyond the piston 50 at each side and are connected by links 64 to crank members 65 secured to a spindle 66. The latter is journalled in a bore 67 (FIG. 5) in the cross beam 51 and therefore is reciprocated with the latter.

The crank members 65 also have integral therewith cam rails 68 which co-operate with rollers 69 of arms 90 which are mounted upon the cap shaped cylinder head 11. The arms 90 are capable of fine adjustment longitudinally with respect to the cylinder head 11 by the aid of eccentric pins 92 carried by spindles 93 associated with an adjustable pointer 94 and stationary dial 95. The pins 92 engage in slots 91 in the arms 90. With this arrangement the exhaust valve 24 is caused to open shortly before the piston 50 reaches the outer end of its stroke with respect to the cylinder sleeve 10 (i.e. the firing stroke), in which position the roller 69 will have come into contact with the inclined portion 68a of the cam' rail 68, thus turning the crank 65 clockwise as viewed in FIG. 7 and opening the valve 24. Said valve will close automatically as the roller 69 moves away from the part 680 of the cam rail 68 on the return stroke.

Means are also advantageously provided to enable the clearance volume of the space 22 to be readily adjusted, for example to suit the type of fuel on which the engine is to be operated from time to time. This means consists in the provision of an adjustable eccentric connecting the head of each link 59 with the crossbeam 51. As shown more clearly in FIGS. 10 to 14 the head of the link 59 is journalled on the eccentic portion 71 of the pin 70 (FIG. 12) which is adapted to be rotatably mounted in the forked end portion of the cross beam 51 (FIG. 13). The enlarged head 72 of the pin 70 is formed with a series of notches 73 (FIGS. 10 and 11) and a locking pin 74 is adapted to be passed through a selected notch 73 and into a recess 74a in the cross beam 51 where it is secured by inserting a split pin 76 when the parts are assembled together, the head 72 being located in the recess 75. Thus, the effective length of each link 59 may be adjusted to the preferred value.

The fuel injection aperture 80 is located centrally in the combustion chamber 22 and fuel oil may be supplied by the pump cylinder 39 at suitable intervals. The construction and operation of the air inlet valve ring 12 is substantially as already described with reference to FIGS. 1 to 4, due allowance being made for the fact that since the cam device 36 may be located further away from the axis of the main piston 5 it may be necessary to interpose an additional gear member between the spindle 40 and the valve ring 12 to transmit the movement of the spindle to said ring.

The cycle of operations of the engine is substantially similar to that describedabove with reference to the engine shown in FIGS. 1 to 4.

. When the main piston 5 is at the end of its stroke to the right as viewed in FIGS. 17 and 18, the auxiliary pistons 50 will then be in or very near the end of their stroke towards the left. On the left of the piston 5 air from the air chest 14 will have admission to the annular compression space 16 past the valve device 13, the valve 18 is closed, but the scavenging valve 20 and the exhaustvalve 24 are open. Thus air entering the combustion space 22 assists in the expulsion of the products of the previous combustion therein and also recharges said space with air. The ports 21 by which the air enters are preferably inclined to cause a swirling motion to the entering air. As the piston 5 commences to move to the left the valves 13 will close, valve 18 will open and valves 24 and 20 will remain open. When the piston 5 hasmoved a short distance the scavenger valve 20 and the exhaust valve 24 will both close. Compression within the cylinder space 22 then commences, while air is also compressed in the annular space 16. As the pistons reach the end of the stroke, and the compression space 22 is reduced to a minimum, fuel is injected into the space 22 and combustion commences as the pistons begin their return stroke. The valve ports 13 open again as the pressure falls in the space 16 and a fresh charge of air is drawn into the air chest 14 and port valves 13 into the space 16, and the valve 18 will close. Towards the end of the return stroke both the valve 20 and the exhaust valve 24 will open, permitting the products of combustion to be discharged by way of the piston 50, assisted by the entry of scavenging air. This completes the cycle; at the same time a similar cycle of operation is taking place to the right of the piston 5, but 180 out of phase therewith.

If the engine is to be driven by petrol fuel instead of Diesel oil fuel the requisite combustion mixture is prepared by carburation of the air in the normal way before its induction into the chest 14, and a sparking plug is located at the aperture 80. Suitable adjustment of the compression ratio and exhaust valve timing is readily effected as already described above.

If. it is desired to employ the engine constructed substantially as described with reference to FIG. 5 as a compressor it is only necessary to remove the auxiliary pistons 50 and associated valve mechanism for the exhaust valve 24 and to replace same by a piston 50 such as shown in FIG. 6 which incorporates a spring loaded exhaust valve 24 It will be understood that the hollow piston 50 is suitably apertured in the skirt or tail to allow the compressed air delivered therethrough to pass out through the sleeve 60 of the guide cover 11 in the same manner as the exhaust gases in the engine employing the piston 50 as previously described above.

The invention is not limited to the case of the particular mechanism above described for connecting to the piston 5 with the crankshaft 30. If desired, for example, the piston may have a driving connection with the crankshaft through the intermediary of a crank, cam, eccentric or the like.

Iclaim:

1. An engine comprising a main cylinder, a doubleacting type piston reciprocatably mounted thereon, a cylinder head detachable mounted on each end of the maincylinder and carrying a cylindrical sleeve of smaller diameter than the main cylinder and extending coaxially towards the main cylinder, a hollow portion of reduced diameter extending coaxially from each end of the main piston to slidably fit within said cylindrical sleeve extending towards it, valve means to control the admission of air to the annular ma in cylinder space surrounding said hollow reduced portion, inlet valve means mounted on said piston to control the admission of air from said annular cylinder space into said hollow portion of the piston, outlet valve means mounted on said piston to control the transfer of air form said hollow piston portion into the interior of said sleeve, and exhaust valve means in the cylinder head to control the discharge of exhaust gas from said sleeve.

2. An engine comprising a main cylinder, a doubleacting type piston reciprocatably mounted thereon, a cylinder head detachably mounted on each end of the main cylinder, a cylindrical sleeve of smaller diameter than the main piston extending coaxially from each cylinder head towards the adjacent face of the main piston, a hollow portion of reduced diameter extending from each face of the main piston to slidably fit within the sleeve extending towards that face, an annular air inlet chest surrounding each of said sleeves, air inlet valve means to control the admission of air from said chest into the annular compression space of the main cylinder encircling each hollow reduced portion of the main piston, an axially disposed spring-loaded poppet valve carried by the main piston to control the admission of air from each of said annular compression spaces into the hollow cylinder portion encircled thereby, an axially disposed spring-loaded poppet valve carried by each said hollow cylinder portion to control the transfer of compressed gaseous fluid from said hollow cylinder portion to the cylindrical sleeve associated therewith and exhaust valve means obturating the discharge of exhaust gases from the interior of said cylindrical sleeve.

3. An engine comprising a main cylinder, a doubleacting type piston reciprocatably mounted thereon, a cylinder head detachably mounted on each end of the main cylinder, a cylindrical sleeve of smaller diameter than the main piston extending coaxially from each cylinder head towards the adjacent face of the main piston, a hollow portion of reduced diameter extending from each face of the main piston to slidably fit within the sleeve extending towards that face, an annular arrangement of air inlet ports between each air chest and the adjacent annular compression space of the main cylinder, a rotatably mounted annular valve plate associated with said air inlet ports, an axially disposed spring-loaded poppet valve carried by the main piston to control the admission of air form each of said annular compression spaces into the hollow cylinder portion encircled thereby, an axially disposed spring-loaded poppet valve carried by each said hollow cylinder portion to control the transfer of compressed gaseous fluid from said hollow cylinder portion to the cylindrical sleeve associated therewith and exhaust valve means obturating the discharge of exhaust gases from the interior of said cylindrical sleeve.

4. An engine comprising a main cylinder, 21 doubleacting type piston reciprocatably mounted thereon, a cylinder head detachably mounted on each end of the main cylinder, a cylindrical sleeve of smaller diameter than the main piston extending coaxially from each cylinder head towards the adjacent face of the main piston, a hollow portion of reduced diameter extending from each face of the main piston to slidably fit within one end of said sleeve adjacent thereto, an auxiliary piston slidably mounted on the other end of each of said sleeves, an annular air inlet chest surrounding each of said sleeves, air inlet valve means to control the admission of air from said chest into the annular compression space of the main cylinder encircling each hollow reduced portion of the main piston, an axially disposed spring-loaded poppet valve carried by the main piston to control the admission of air from each of said annular compression spaces into the hollow cylinder portion encircled thereby, an axially disposed spring-loaded poppet valve carried by each said hollow cylinder portion to control the transfer of compressed gaseous fluid from said hollow cylinder portion to the cylindrical sleeve associated therewith, exhaust valve means carried by each of said sleeves to obturate the discharge of exhaust gas therefrom, and means for actuating said exhaust valves and air inlet valve in unison with the reciprocating movement of the piston.

5. An engine comprising a main cylinder, a doubleacting type piston reciprocatably mounted thereon, a cylinder head detachably mounted on each end of the main cylinder, a cylindrical sleeve of smaller diameter than the main piston extending coaxially from each cylinder head towards the adjacent face of the main piston, a hollow portion of reduced diameter extending from each face of the main piston to slidably fit within one end of said sleeve adjacent thereto, an auxiliary piston slidably mounted on the other end of each of said sleeves, an annular air inlet chest surrounding each of said sleeves, air inlet valve means to control the admission of air from said chest into the annular compression space of the main cylinder encircling each hollow reduced portion of the main piston, an axially disposed spring-loaded poppet valve carried by the main piston to control the admission of air from each of said annular compression spaces into the hollow cylinder portion encircled thereby, an axially disposed spring-loaded poppet valve carried by each said hollow cylinder portion to control the transfer of compressed gaseous fluid from said hollow cylinder portion to the cylindrical sleeve associated therewith, exhaust valve means carried by each of said sleeves to obturate the discharge of exhaust gas therefrom, means for actuating said exhaust valves and air inlet valves in unison with the reciprocating movement of the piston,-and means for adjusting the timing of said exhaust valves.

6. An engine comprising a main cylinder, a doubleacting type piston reciprocatably mounted therein, a crank bearing block transversely slidable in said piston intermediately between the opposite ends of the piston, a crankshaft directly mounted in said bearing block, a cylinder head detachably mounted on each end of the main cylinder and carrying a cylindrical sleeve of smaller diameter than the main cylinder and extending coaxially towards the adjacent face of the piston, a hollow portion of reduced diameter extending coaxially from each end of the main piston to slidably fit within said cylindrical sleeve extending towards it, valve means to control the admission of air to the annular main cylinder space surrounding said hollow reduced portion, inlet valve means mounted on said piston to control the admission of air from said annular cylinder space into said hollow portion of the piston, outlet valve means mounted on said piston to control the transfer of air from said hollow piston portion into the interior of said sleeve, and exhaust valve means in the cylinder head to control the discharge of exhaust gas from said sleeve.

7. An engine comprising a main cylinder, a doubleacting type piston reciprocatably mounted therein, a crank bearing block transversely slidable in said piston intermediately between the opposite ends of the piston, a crankshaft directly mounted in said bearing block, a cylinder head detachably mounted on each end of the main cylinder, a cylindrical sleeve of smaller diameter than the main piston extending coaxially from each cylinder head towards the adjacent face of the main piston, a hollow portion of reduced diameter extending from each face of the main piston to slidably fit within one end of said sleeve adjacent thereto, an auxiliary piston slidably mounted in the other end of each of said sleeves, yoke and connecting rod means operatively connecting the crankshaft with the auxiliary pistons to coordinate the movement thereof in relation to the movement of the main piston so that during the major part of these operations they move respectively in opposite directions, an annular air inlet chest surrounding each of said sleeves, air inlet valve means to control the admission of air from said chest into the annular compression space of the main cylinder encircling each hollow reduced portion of the main piston, an axially disposed spring-loaded poppet valve carried by the main piston to control the admission of air from each of said annular compression spaces into the hollow cylinder portion encircle thereby, an axially disposed spring-loaded poppet valve carried by each of said hollow cylinder portion to control the transfer of compressed gaseous fluid from said hollow cylinder portion to the cylindrical sleeve associated therewith, and means operatively connnected with the carnkshaft for actuating said exhaust valves and air inlet valves in unison with the reciprocating movement of the piston.

8. An engine comprising a main cylinder, a doubleacting type piston reciprocatably mounted therein, a crank bearing block transversely slidable in said piston intermediately between the opposite ends of the piston, a crankshaft directly mounted in said bearing block, a cylinder head detachably mounted on each end of the main cylinder, a cylindrical sleeve of smaller diameter than the main piston extending coaxially from each cylinder head towards the adjacent face of the main piston, a hollow portion of reduced diameter extending from each face of the main piston to slidably fit within one end of said sleeve adjacent thereto, an auxiliary piston slidably mounted in the other end of each of said sleeves, yoke and connecting rod means operatively connecting the crankshaft with the auxiliary pistons to coordinate the movement thereof in relation to the movement of the main piston so that during the major part of these operations they move respectively in opposite directions, means for finely adjusting the positions of the auxiliary pistons in relation to that of the main piston, an annular air inlet chest surrounding each of said sleeves, air inlet valve means to control the admission of air from said chest into the annular compression space of the main cylinder encircling each hollow reduced portion of the main piston, an axially disposed spring-loaded poppet valve carried by the main piston to control the admission of air from each of said annular compression spaces into the hollow cylinder portion encircled thereby, an axially disposed spring-loaded poppet valve carried by each said hollow cylinder portion to control the transfer of compressed gaseous fluid from said hollow cylinder portion to the cylindrical sleeve associated therewith, and means operatively connected with the crankshaft for actuating said exhaust valves and air inlet valves in unison with the reciprocating movement of the piston. 

1. An engine comprising a main cylinder, a double-acting type piston reciprocatably mounted thereon, a cylinder head detachable mounted on each end of the main cylinder and carrying a cylindrical sleeve of smaller diameter than the main cylinder and extending coaxially towards the main cylinder, a hollow portion of reduced diameter extending coaxially from each end of the main piston to slidably fit within said cylindrical sleeve extending towards it, valve means to control the admission of air to the annular main cylinder space surrounding said hollow reduced portion, inlet valve means mounted on said piston to control the admission of air from said annular cylinder space into said hollow portion of the piston, outlet valve means mounted on said piston to control the transfer of air form said hollow piston portion inTo the interior of said sleeve, and exhaust valve means in the cylinder head to control the discharge of exhaust gas from said sleeve.
 2. An engine comprising a main cylinder, a double-acting type piston reciprocatably mounted thereon, a cylinder head detachably mounted on each end of the main cylinder, a cylindrical sleeve of smaller diameter than the main piston extending coaxially from each cylinder head towards the adjacent face of the main piston, a hollow portion of reduced diameter extending from each face of the main piston to slidably fit within the sleeve extending towards that face, an annular air inlet chest surrounding each of said sleeves, air inlet valve means to control the admission of air from said chest into the annular compression space of the main cylinder encircling each hollow reduced portion of the main piston, an axially disposed spring-loaded poppet valve carried by the main piston to control the admission of air from each of said annular compression spaces into the hollow cylinder portion encircled thereby, an axially disposed spring-loaded poppet valve carried by each said hollow cylinder portion to control the transfer of compressed gaseous fluid from said hollow cylinder portion to the cylindrical sleeve associated therewith and exhaust valve means obturating the discharge of exhaust gases from the interior of said cylindrical sleeve.
 3. An engine comprising a main cylinder, a double-acting type piston reciprocatably mounted thereon, a cylinder head detachably mounted on each end of the main cylinder, a cylindrical sleeve of smaller diameter than the main piston extending coaxially from each cylinder head towards the adjacent face of the main piston, a hollow portion of reduced diameter extending from each face of the main piston to slidably fit within the sleeve extending towards that face, an annular arrangement of air inlet ports between each air chest and the adjacent annular compression space of the main cylinder, a rotatably mounted annular valve plate associated with said air inlet ports, an axially disposed spring-loaded poppet valve carried by the main piston to control the admission of air form each of said annular compression spaces into the hollow cylinder portion encircled thereby, an axially disposed spring-loaded poppet valve carried by each said hollow cylinder portion to control the transfer of compressed gaseous fluid from said hollow cylinder portion to the cylindrical sleeve associated therewith and exhaust valve means obturating the discharge of exhaust gases from the interior of said cylindrical sleeve.
 4. An engine comprising a main cylinder, a double-acting type piston reciprocatably mounted thereon, a cylinder head detachably mounted on each end of the main cylinder, a cylindrical sleeve of smaller diameter than the main piston extending coaxially from each cylinder head towards the adjacent face of the main piston, a hollow portion of reduced diameter extending from each face of the main piston to slidably fit within one end of said sleeve adjacent thereto, an auxiliary piston slidably mounted on the other end of each of said sleeves, an annular air inlet chest surrounding each of said sleeves, air inlet valve means to control the admission of air from said chest into the annular compression space of the main cylinder encircling each hollow reduced portion of the main piston, an axially disposed spring-loaded poppet valve carried by the main piston to control the admission of air from each of said annular compression spaces into the hollow cylinder portion encircled thereby, an axially disposed spring-loaded poppet valve carried by each said hollow cylinder portion to control the transfer of compressed gaseous fluid from said hollow cylinder portion to the cylindrical sleeve associated therewith, exhaust valve means carried by each of said sleeves to obturate the discharge of exhaust gas therefrom, and means for actuating said exhaust valves and air inlet valve in unison with the reciprocating movement of the piston.
 5. An enginE comprising a main cylinder, a double-acting type piston reciprocatably mounted thereon, a cylinder head detachably mounted on each end of the main cylinder, a cylindrical sleeve of smaller diameter than the main piston extending coaxially from each cylinder head towards the adjacent face of the main piston, a hollow portion of reduced diameter extending from each face of the main piston to slidably fit within one end of said sleeve adjacent thereto, an auxiliary piston slidably mounted on the other end of each of said sleeves, an annular air inlet chest surrounding each of said sleeves, air inlet valve means to control the admission of air from said chest into the annular compression space of the main cylinder encircling each hollow reduced portion of the main piston, an axially disposed spring-loaded poppet valve carried by the main piston to control the admission of air from each of said annular compression spaces into the hollow cylinder portion encircled thereby, an axially disposed spring-loaded poppet valve carried by each said hollow cylinder portion to control the transfer of compressed gaseous fluid from said hollow cylinder portion to the cylindrical sleeve associated therewith, exhaust valve means carried by each of said sleeves to obturate the discharge of exhaust gas therefrom, means for actuating said exhaust valves and air inlet valves in unison with the reciprocating movement of the piston, and means for adjusting the timing of said exhaust valves.
 6. An engine comprising a main cylinder, a double-acting type piston reciprocatably mounted therein, a crank bearing block transversely slidable in said piston intermediately between the opposite ends of the piston, a crankshaft directly mounted in said bearing block, a cylinder head detachably mounted on each end of the main cylinder and carrying a cylindrical sleeve of smaller diameter than the main cylinder and extending coaxially towards the adjacent face of the piston, a hollow portion of reduced diameter extending coaxially from each end of the main piston to slidably fit within said cylindrical sleeve extending towards it, valve means to control the admission of air to the annular main cylinder space surrounding said hollow reduced portion, inlet valve means mounted on said piston to control the admission of air from said annular cylinder space into said hollow portion of the piston, outlet valve means mounted on said piston to control the transfer of air from said hollow piston portion into the interior of said sleeve, and exhaust valve means in the cylinder head to control the discharge of exhaust gas from said sleeve.
 7. An engine comprising a main cylinder, a double-acting type piston reciprocatably mounted therein, a crank bearing block transversely slidable in said piston intermediately between the opposite ends of the piston, a crankshaft directly mounted in said bearing block, a cylinder head detachably mounted on each end of the main cylinder, a cylindrical sleeve of smaller diameter than the main piston extending coaxially from each cylinder head towards the adjacent face of the main piston, a hollow portion of reduced diameter extending from each face of the main piston to slidably fit within one end of said sleeve adjacent thereto, an auxiliary piston slidably mounted in the other end of each of said sleeves, yoke and connecting rod means operatively connecting the crankshaft with the auxiliary pistons to coordinate the movement thereof in relation to the movement of the main piston so that during the major part of these operations they move respectively in opposite directions, an annular air inlet chest surrounding each of said sleeves, air inlet valve means to control the admission of air from said chest into the annular compression space of the main cylinder encircling each hollow reduced portion of the main piston, an axially disposed spring-loaded poppet valve carried by the main piston to control the admission of air from each of said annular compression spaces into the hollow cylinder portion encircle Thereby, an axially disposed spring-loaded poppet valve carried by each of said hollow cylinder portion to control the transfer of compressed gaseous fluid from said hollow cylinder portion to the cylindrical sleeve associated therewith, and means operatively connnected with the carnkshaft for actuating said exhaust valves and air inlet valves in unison with the reciprocating movement of the piston.
 8. An engine comprising a main cylinder, a double-acting type piston reciprocatably mounted therein, a crank bearing block transversely slidable in said piston intermediately between the opposite ends of the piston, a crankshaft directly mounted in said bearing block, a cylinder head detachably mounted on each end of the main cylinder, a cylindrical sleeve of smaller diameter than the main piston extending coaxially from each cylinder head towards the adjacent face of the main piston, a hollow portion of reduced diameter extending from each face of the main piston to slidably fit within one end of said sleeve adjacent thereto, an auxiliary piston slidably mounted in the other end of each of said sleeves, yoke and connecting rod means operatively connecting the crankshaft with the auxiliary pistons to coordinate the movement thereof in relation to the movement of the main piston so that during the major part of these operations they move respectively in opposite directions, means for finely adjusting the positions of the auxiliary pistons in relation to that of the main piston, an annular air inlet chest surrounding each of said sleeves, air inlet valve means to control the admission of air from said chest into the annular compression space of the main cylinder encircling each hollow reduced portion of the main piston, an axially disposed spring-loaded poppet valve carried by the main piston to control the admission of air from each of said annular compression spaces into the hollow cylinder portion encircled thereby, an axially disposed spring-loaded poppet valve carried by each said hollow cylinder portion to control the transfer of compressed gaseous fluid from said hollow cylinder portion to the cylindrical sleeve associated therewith, and means operatively connected with the crankshaft for actuating said exhaust valves and air inlet valves in unison with the reciprocating movement of the piston. 